1. Field of the Invention
The present invention relates to a technique that determines a viewpoint position of a virtual camera when multiple characters exist in a virtual three-dimensional space in a three-dimensional video game.
2. Description of the Related Art
In a role playing game (RPG), a battle between player characters and enemy characters is generally performed in the process of the game. In the case of a three-dimensional video game, the state of the battle is perspective-transformed by a virtual camera provided on a battle field (battle map) and displayed on a display screen. A player can recognize the state of the game from only an image on the display screen.
In the conventional RPG, the image displayed on the display screen was generated by perspective-transforming a virtual three-dimensional space where the battle was performed by the virtual camera placed at a predetermined position. Regarding the position of the virtual camera, there was a fixed position and a moving position. Movement of the position of the virtual camera was performed by changing the position of the virtual camera to multiple predetermined positions, sequentially. The image projected from the same position was repeatedly displayed on the display screen, so that a change in the display screen becomes monotonous.
There is disclosed a technique of moving a viewpoint position of a virtual camera in a three-dimensional video game though this is not considered as an application to a battle in an RPG. Unexamined Japanese Patent Publication 2001-162040 discloses a technique in which a player presses an operation button corresponding to a mark with an allocated camera angle to change a viewpoint position of a virtual camera. Unexamined Japanese Patent Publication 10-113467 discloses a technique in which the position of a virtual camera is changed according to a player's viewpoint and an outside spectator's viewpoint.
However, in the technique disclosed in Unexamined Japanese Patent Publication 2001-162040, the viewpoint position of the virtual camera moves to only a predetermined position. This technique cannot solve the problem that a change in the display screen becomes monotonous. In the technique disclosed in Unexamined Japanese Patent Publication 10-113467, the viewpoint position of the virtual camera can freely move. The movement can be attained by only following one object (player (car) in this case).
On the contrary, the battle in an RPG cannot be established unless at least two characters including one player character and one enemy character exist. In the RPG battle, three or more characters exist in many cases. If the technique disclosed in Unexamined Japanese Patent Publication 10-113467 is used, the viewpoint position of the virtual camera moves with the movement of any one of the characters. In this case, the positions of the characters are one-sided and displayed on the display screen and some of the characters are not projected on the display screen in some cases.
If the viewpoint position of the virtual camera is set in a way to project the entire movement range of the characters participating in the battle, the problem that some of the characters are not projected on the display screen is eliminated. However, there is a problem that each character may be displayed small or the characters may be displayed on one-side according to the position where the character moved.